This application proposes to develop a user-friendly computer software package for the statistical analysis of event time data ('survival' time data) in clinical trials and observational cohort studies. If successful, this effort would result in the availability of the major statistical methodologies for clinical trials in a form that is powerful and easy to use on a wide variety of mini- and micro-computers. Emphasized in the proposed development will be: (a) user-friendliness, (b) the flexibility to perform all the key analyses use in the analysis of clinical trials and observational prospective studies, and (c) portability among the new generation of powerful mini- and micro-computers. With these objectives, this software package would have applicability and use in both government-sponsored and privately-sponsored clinical trials and observational prospective studies. This proposed effort is pertinent to those programs within NIH which use clinical trial or cohort study methodology. To streamline this effort, it is proposed: (a) to use as a starting point existing programs and subroutines, many of which have been developed by the proposers, and (b) to design the software package in logically separate modules (analysis modules, data maintenance modules, and user interface modules). A potential commercial application of this proposed effort is the distribution of the software package, perhaps under a contractual arrangement with an appropriate distributor of scientific software. The demand for such a package is expected to be high because of: (a) the increasing use of the clinical trial and follow-up study methodology, notably in cancer research and in heart disease research, and (b) the proliferation of a new generation of computers that are both powerful and inexpensive, thus bringing computing within reach of a broad spectrum of users, including clinicians, biostatisticians and teachers.